Posts Tagged ‘Fossil species roll call’

Spheniscus penguins are your basic model. Collectively, the four living species are sometimes known as “tuxedo penguins” for their striking color patterns, which resemble a tuxedo motif just a bit more than those of other types of penguins. These four species are among the most warm-weather adapted of modern penguins, and live in Africa, South America and the Galapagos Islands. Spheniscus penguins also have a really good fossil record, with lots of skeletons discovered in the past few years in places like Peru and Chile. Many of these specimens are very similar to the living Humboldt Penguin (Spheniscus humboldti), which plies the coasts of South America today. However, two species stand out for their remarkable appearance.

Spheniscus urbinai and Spheniscus megaramphus were discovered in the prolific fossil deposits of the Peruvian Atacama Desert (also referred to a the Sechura Desert). These penguins appear to be standard, although slightly larger, versions of the basic Spheniscus plan from the toes up the neck. Flippers, legs, vertebrae – all these bones are not easily distinguishable from the same elements in a Humboldt Penguin to the untrained eye. The head, though, is a different story. These two penguins have “bobble heads” – skulls that are proportionally too big for their body. Well, too big for a normal penguin’s body anyway – no one seems to have sent a memo to Spheniscus urbinai or Spheniscus megaramphus. Aside from the big heads, these penguins had killer beaks. The tips, instead of being straight like many fossil penguins or lightly down-turned like most modern species, were powerfully developed into a sharp menacing hook. This is a style of beak often seen in aeriel predators like eagles and fish-snatching birds like frigatebirds.

One of the basic facts about fossil bird beaks is that they tend to tell only half the story. That is because the bony part of the beak is covered by a layer of keratin in life. This sheath can greatly extend the tip of the bill in some species, and Spheniscus penguins are a perfect example. The bony beaks of these birds have a modest sharp hook at the tip. When the sheath is added though, the tips start looking pretty fierce. Adding the keratin layer to Spheniscus urbinai and Spheniscus megaramphus would rachet up the beak from menacing to downright scary. What were these fossil species doing with there intimidating beaks? Most likely catching tough prey. A powerful hook would be well suited to ripping into fish and squid, and is more useful for holding onto a larger victim than gathering up tiny things like sardines. Whatever their ecology, the bobble-headed Spheniscus species did not make it to the present day. After splitting off from the main Spheniscus lineage around 6 million years ago, Spheniscus urbinai and Spheniscus megaramphus enjoined a few million years of successful hunting before vanishing.

A crude rendering of the body outline of Spheniscus urbinai with a living Spheniscus penguin for scale.

Today, two new fossil penguin species formally enter the scientific catalog. These 27 million year old penguins are unique, “svelte” species with graceful proportions discovered in New Zealand. I worked on these incredible fossils in 2009 and 2011 with Dr. Ewan Fordyce of the University of Otago and former Otago students Dr. Tatsuro Ando and Dr. Craig Jones (now at the Ashoro Museum of Paleontology and Institute of Geological and Nuclear Sciences, respectively) on a scientific article describing the new species and the new details they reveal about penguin evolution. Our findings are now published in the latest issue of the Journal of Vertebrate Paleontology.

So, what makes Kairuku so special? The three skeletons discovered are among the most complete ever recovered for an ancient penguin. They reveal that Kairuku penguins cut a striking figure. They had more slender proportions than living penguins, with an elongate trunk, narrow bill, and long, narrow wing bones. The legs, on the other hand, were quite robust. Overall, the skeleton conveys a very elegant bird, sleek yet powerful. And, they were tall. A standing Kairuku penguin would have reached about 4 feet 2 inches, more than a foot taller than an Emperor Penguin. Artist Chris Gaskin created a meticulous reconstruction of the new species that really drives these features home. You can practically feel the wind whipping sand and ocean spray into the air as the two penguins come ashore.

Two Kairuku penguins come ashore, passing a stranded Waipatia dolphin. Artwork by Chris Gaskin, owner and copyright owner: Geology Museum, University of Otago. Used with permission.

The name Kairuku is taken from Maori language, and loosely translates to “diver who returns with food”. Kairuku waitaki is named for the large river that flows through modern Canterbury and Otago. Kairuku grebneffi is named in honor of the late Andrew Grebneff, who contributed to the field collection and preparation of many of the fossil specimens of both species.

The first Kairuku specimens were discovered by the great New Zealand zoologist and paleontologist Dr. Brian J. Marples in the 1940s, but these bones were not immediately recognized as belonging to a new species because they were not very well preserved and typically included only a few pieces of the wing skeleton. Highly complete skeletons were later recovered by Dr. Ewan Fordyce, starting with a wonderful discovery along the banks of the Waihao River in 1977. This skeleton, a beautiful set of orange fossil bones embedded in soft greensand matrix, would turn out to be the holotype specimen of Kairuku – the standard by which all Kairuku specimens shall henceforth be compared to. Over the next 35 years, many more Kairuku specimens have been found. In fact, the most recent was collected only two months ago during our field excursion in New Zealand.

Inguza is fast becoming one of my favorite fossil penguins. Last December, I spent several weeks in South Africa studying fossil penguin bones in museums and at field sites with my friend and colleague Daniel Thomas. Much of our time was spent examining, measuring, and analyzing bones of a somewhat runty penguin named Inguza predemersus. This species was on the small end of the scale, and would have stood about chin-high next to the living Blackfooted Penguin (a species that is also known as the Jackass Penguin or the African Penguin). Bones of Inguza are very common in the Langebaanweg Quarry, a famous fossil site that has produced some of the most amazing fossils in Africa, including the remains of a miraculous short-necked giraffe and Africa’s first fossil bear (completely unexpected as no bears live on the continent today). Daniel Thomas and I were able to learn a lot about the evolutionary history of African penguins by studying Inguza, and I’ll post more about that soon.

Holding the bones of Inguza side by side with bones from modern Blackfooted Penguins, I often wondered whether the two had ever met. Among the hundreds of penguin bones from the Langebaanweg quarry, there is no trace of Blackfooted Penguin remains. The youngest Inguza fossils are about 5.1 million years old, and the oldest Blackfooted Penguin bones are between 250,000 and 400,000 years old. There’s a pretty large gap in the African fossil record between these points though, where few marine birds of any sort are known. It’s possible that at some time within that interval, the last Inguza individuals noticed a new neighbor in their colonies as the founding Blackfooted Penguin population arrived. Perhaps they lived side by side, choosing different prey. Perhaps they jostled uneasily for nesting sites. Perhaps the new arrivals even contributed to the extinction of Inguza by outcompeting that species.

Or, its possible the last Inguza died out before any Blackfooted Penguins set foot in Africa. In the most extreme scenario, there may have been NO penguins at all in Africa at some point 1-4 million years ago. Blackfooted Penguins could have arrived into a “penguin vacuum” and set up shop wherever they pleased. Not knowing what happened is one of the reasons we keep going back to the field to collect more fossils. As we fill in the blank parts of the record, we will come closer to understanding what actually happened on those beaches millions of years ago.

Korora is the name for the living Little Blue Penguin in Maori. It is also the genus name of one of the smallest fossil penguins, chosen to indicate the animal’s small stature.

Korora oliveri is not the smallest fossil penguin ever discovered – that honor belongs to Ereticus tonnii. In fact, Korora oliveri would probably have stood about as tall as your average aquarium Humboldt penguin, although this estimate is not very exact because this species is only known from a single bone. Korora is remarkable because the fossil record of penguins is dominated by larger taxa. The vast majority of fossil penguins were at least as big as the King Penguin. Very few small species are known until we reach the more recent geological epochs.

Korora lived in New Zealand during the late Oligocene, about 25 million years ago. It swam alongside giants – most of the other penguins known from this area and time are huge, towering creatures including some of the largest that ever lived. It seems like smaller penguins were very rare in the area – as more and more large penguin fossils have been harvested from the relevant rocks they overwhelmingly belong to large species. This suggests that penguins focused on a different niche in the Oligocene. Most species probably were eating larger fish and sitting higher up the food chain, playing a role more like that of seals than modern penguins.

Korora remains a puzzle for penguin paleontologists. With only a single specimen, it is very difficult to figure out where this species belongs in the penguin evolutionary tree. If it turns out to be closely related to its larger contemporaries, then it would provide evidence for dwarfing in an ancient penguin lineage – perhaps downsizing from its ancestors in order to exploit smaller prey. If, on the other hand, Korora is more closely related to living penguins than these large taxa, it may be the herald of the modern penguin radiation – smaller, avoiding direct competition with marine mammals, perhaps more specialized for catching krill than fish. Trying to determine which of these hypotheses is correct is futile at the moment – we need more fossils to even start understanding what this penguin ate or how modern its skeleton was. This is why paleontology is such an exciting science. Some questions can be answered by more work, others only by new discoveries. Korora awaits the latter.

Many of the most heralded discoveries of fossil penguins are from giant species. Not all extinct penguins were large, however, and a few were quite tiny. The smallest fossil species yet discovered belongs to a diminutive penguin from the Miocene (about 22 million years ago) of Argentina. George Simpson described this fossil in one of his last scientific publications on fossil penguins in 1981. The first specimen was a tarsometatarsus (that foot bone that keeps popping up in penguin paleontology) and some wing bones have subsequently come to light.

The fossil in question was originally given the genus name Microdytes, meaning “tiny diver”. However, this name is now obsolete because an even tinier diver – a beetle – already had claim on the name “Microdytes“. Beetles have a pesky habit of preoccupying names applied to vertebrates. To be more accurate, vertebrate paleontologists don’t always thoroughly check all taxonomic records before naming new fossils. The most famous example is the case of the theropod dinosaur Syntarsus. This genus name was already occupied by a Malagasy beetle, and so some entomologists took it upon themselves to create a new name for the dinosaur: Megapnosaurus. This translates to “big dead lizard”, a probable sling at the overly generous share of public interest dinosaurs receive compared to beetles.In a zoological wild west, a penguin might be able to bully a beetle out of a prime name. However, that’s not the way things work in the real world. The rule of priority means that the first species to be given a name in a formal scientific publication keeps it. So Microdytes stays with the beetle. The penguin was thus re-christened Eretiscus by Storrs Olson, who first noticed the conflict. The new name means “tiny rower” in reference to the penguins flipper-based locomotion.

Eretiscus was very small. The Little Blue Penguin is the smallest living penguin, reaching only about 1kg in weight – a virtual rubber duck in size (and squeak). At only about 1.5 feet tall, these little guys are less than knee high on most humans. Originally, Eretiscus tonnii was reported as being even smaller. However, only one skeleton of the modern Little Blue was available for comparison when Simpson described the fossil find. The tarsometatarsus of Eretiscus was a millimeter and a half smaller than the tarsometatarsus of that Little Blue skeleton, but other smaller skeletons exist in collections of museums. So the fossil was not the smallest individual penguin ever, but the species may well have been the smallest (we don’t have enough samples to figure out the average). Quibbling over records aside, we can say that small penguins have been around for a long time. They don’t seem to have been very common though. Only a few fossil bones of penguins in the Little Blue size range have been discovered worldwide versus thousands of bones of average size to giant penguins.

A humerus (wing bone) from Eretiscus tonnii

References:

Simpson, G.G. 1981. Notes on some fossil penguins, including a new genus from Patagonia. Ameghiniana 18: 266–272.

Island birds have undergone some of the most fascinating radiations in evolutionary history, producing such wonders as the “toothed” Moa-Nalo ducks (Chelychelynechen, Thambetochen and Ptaiochen) of Hawaii and the enormous nine foot tall Elephant Birds (Aepyornis) of Madagascar. Island birds have also been devastated by human exploitation. The Dodo (Raphus), once an inhabitant of Mauritius, is an icon of extinction. Sadly, the Dodo is only the most well-known member of this club. Giant moa were hunted to extinction in New Zealand. Dozens of unique birds including Moa-Nalos, flightless ibises and nectar-feeding songbirds were wiped off the Hawaiian Islands following the arrival of humans. Today, many of the native bird species of Guam are severely endangered by predation by invasive snakes, introduced by humans.

Penguins were long thought to have been exempt from this fate. Because they can retreat to the sea where they are difficult to capture, penguins are somewhat less vulnerable to hunting than many other types of birds, particularly other flightless ones. Although historically harassed by humans in many ways, no penguin species was thought to have been wiped out until a very recent discovery. A team of researchers in New Zealand and Australia rounded up subfossil bones from archeological sites from the South Island of New Zealand ranging from 200 to 1500 years in age. They extracted ancient DNA from the bones and compared the sequences to other collected from live Yellow-Eyed Penguins (and museum specimens of the same species). The findings were startling – a wide genetic distance was uncovered separating the pre-1500s mainland penguin bones from post-1500s bones. The younger bones belong to the modern Yellow-Eyed Penguin (Megadyptes antipodes), and their DNA sequences cluster with samples from living individuals and subfossil bones of the species from outside the mainland. However, DNA from the pre-1500s subfossil bones from the mainland don’t cluster with the Yellow-eyed Penguin samples. DNA evidence suggests a distinct species of penguin was living on the South Island of New Zealand. This conclusion is backed up by careful comparisons of the bones, which demonstrates size and shape differences outside the range of normal variation seen in living Yellow-Eyed Penguins. The newly recognized, recently extinct species was named Megadyptes waitaha by the team.

Bones of the living Yellow-Eyed Penguin Megadyptes antipodes (left side of each pair) and the recently extinct Megadyptes waitaha (right side of each pair).

Dating of the fossil deposits suggests that Megadyptes waitaha survived all the way up to the time of colonization, overlapping with the fist human settlers to arrive from Polynesia. Direct evidence from associated artifacts shows that humans actively hunted these penguins, and the circumstantial evidence from timing strongly points to overexploitation as the proximal cause of their extinction. A second interesting finding of this study is that the modern Yellow-eyed Penguin seems to have benefited from the extinction of Megadyptes waitaha. Comparisons of the morphology of subfossil penguin bones, along with DNA extraction, reveals that in the 1500s the Yellow-eyed Penguin was restricted to sub-Antarctic islands such as the Auklands. During this same time period, Megadyptes waitaha inhabited a wide swath of the east coast of the South Island. Flash forward to 1800, and Megadyptes waitaha is nowhere to be found anywhere. Yellow-eyed Penguins crop up nearly everywhere that Megadyptes waitaha used to be. The timing suggests that as hunting patterns shifted, prime penguin real estate vacated by Megadyptes waitaha was reclaimed by Megadyptes antipodes.

So, Megadyptes waitaha is now a ghost on our collective consciences. These bones are something to think of when penguin populations suffer from oil spills, rampaging stray dogs, or overdeveloped beaches. There were at least 20 species of penguins when humans first appeared, and now we have 19 species left to enjoy and protect.

South Africa, host of the next World Cup, is one of the best places on Earth to see penguins in the wild. Only one species of penguin lives there today (the Jackass Penguin Spheniscus demersus), but it is possible to visit quite up close with these charming birds. The Jackass Penguin earns its name for its abrasive braying call rather than any foolhardy behavior. Historically, this species has place of pride as the first penguin to be encountered by European explorers. This momentous occasion occurred as Vasco da Gama’s voyage around the Cape of Good Hope landed for supplies near present day Mossel Bay in 1497 (of course, native peoples in South America, Africa, New Zealand and Australia were certainly well aware of penguins for hundreds if not thousands of years prior to this encounter). It is not recorded how the penguins greeted their strange visitors, but the humans behaved as customary when encountering wondrous new life forms by plundering a good number of them to eat. Relations have since improved between our species and theirs, and Jackass Penguins are a fixture at many aquariums and zoos worldwide.

While Spheniscus demersus is the only species surviving on the coast of Africa today, several fossil species have been described. Interestingly enough, all South African penguins are from the Miocene-Pleistocene Epochs – substantially younger than the oldest fossils from other continents. Whether penguins arrived to Africa late, or we simply have not searched diligently enough for them in older rocks, remains to be seen. One interesting and fortuitous fossil discovery from South Africa was the unearthing of Nucleornis insolitus during excavations for the Koeberg nuclear power station. Geroge Gaylord Simpson, featured in the last post, named the species in 1979. The etymology of the genus name should be obvious. Unfortunately only two foot bones – tarsometatarsi in avian anatomical lingo – were found. Because the purpose of the excavation was to sink a foundation for the power plant, not search for penguin fossils, little effort was devoted to deciphering the age of the rocks in which the penguin bones were found. They are thought to be Miocene in age – roughly between 5 and 23 million years old, and probably closer to the lower end of that range. Very little is known about Nucleornis insolitus because we have so little of the skeleton. Based on the foot bones, the species was comparable to the living Jackass Penguin in size. In all of the preserved morphological details, the tarsometatarsus resembles that of living penguins. While it is not possible to definitively say whether Nucleornis shared the most recent common ancestor as the living penguin species, it was at least very closely related. These scraps of fossil represent one piece of the puzzle of how penguins arrived and radiated in Africa, but much more work remains to be done before we will understand the whole story.

References:

Simpson, G.G. 1979. A new genus of Late Tertiary penguin from Langebaanweg, South Africa. Annals of the South African Museum 78: 1–9.

March of the Fossil Penguins

written by Dr. Daniel Ksepka

This blog details fossil discoveries and research on the fascinating Sphenisciformes. The aim is to introduce the cast of fossil species (50 and counting), explore the evolutionary history of penguin bones, feathers and ecology, and explain how scientists learn about life in the past.